Not all letters have superscript or subscript counterparts. The counterparts are from different ranges, so might not look nice when next to each other.
I think 20th using Unicode lowercase superscript looks ugly 20ᵗʰ. With uppercase superscript it is somewhat OK: 20ᵀᴴ.
The list is from [WayBack] javascript – How to find the unicode of the subscript alphabet? – Stack Overflow:
Take a look at the wikipedia article Unicode subscripts and superscripts. It looks like these are spread out across different ranges, and not all characters are available.
Consolidated for cut-and-pasting purposes, the Unicode standard defines complete sub- and super-scripts for numbers and common mathematical symbols ( ⁰ ¹ ² ³ ⁴ ⁵ ⁶ ⁷ ⁸ ⁹ ⁺ ⁻ ⁼ ⁽ ⁾ ₀ ₁ ₂ ₃ ₄ ₅ ₆ ₇ ₈ ₉ ₊ ₋ ₌ ₍ ₎ ), a full superscript Latin lowercase alphabet except q ( ᵃ ᵇ ᶜ ᵈ ᵉ ᶠ ᵍ ʰ ⁱ ʲ ᵏ ˡ ᵐ ⁿ ᵒ ᵖ ʳ ˢ ᵗ ᵘ ᵛ ʷ ˣ ʸ ᶻ ), a limited uppercase Latin alphabet ( ᴬ ᴮ ᴰ ᴱ ᴳ ᴴ ᴵ ᴶ ᴷ ᴸ ᴹ ᴺ ᴼ ᴾ ᴿ ᵀ ᵁ ⱽ ᵂ ), a few subscripted lowercase letters ( ₐ ₑ ₕ ᵢ ⱼ ₖ ₗ ₘ ₙ ₒ ₚ ᵣ ₛ ₜ ᵤ ᵥ ₓ ), and some Greek letters ( ᵅ ᵝ ᵞ ᵟ ᵋ ᶿ ᶥ ᶲ ᵠ ᵡ ᵦ ᵧ ᵨ ᵩ ᵪ ). Note that since these glyphs come from different ranges, they may not be of the same size and position, depending on the typeface.
After a nice chat with my nephew EWD, I did some research and found the above via
- [WayBack] macOS Character Viewer – NSHipster
- [WayBack] Use subscripts in text- rd, th, st – Apple Community
–jeroen